Locally commensurate charge-density wave with three-unit-cell periodicity in YBa₂Cu₃O_y

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Materials

Background:

• Understanding charge-density waves (CDWs) is crucial for cuprate superconductors.
• Distinguishing generic from material-dependent CDW properties is key.

Purpose of the Study:

• To identify the mechanism of charge-density wave formation in cuprate superconductors.
• To elucidate the generic microscopic structure of CDWs.

Main Methods:

• Nuclear Magnetic Resonance (NMR) spectroscopy was used to probe the local structure of CDWs.
• Analysis focused on YBa2Cu3Oy, a representative cuprate superconductor.

Main Results:

• Long-range CDW order in YBa2Cu3Oy is unidirectional with a commensurate period of three unit cells (λ=3b).
• NMR spectra indicate a dominant oxygen character of the CDW.
• No evidence for a secondary CDW with λ=6b, associated with a pair-density wave, was found.

Conclusions:

• The incommensurability observed in X-ray scattering arises from phase slips.
• The spatial profile of cuprate CDWs results from a balance between long-range incommensurate tendencies and local commensuration effects.
• These findings highlight universal features of CDWs in cuprate superconductors.